1. Field of the Invention
The present invention relates to a method of removing air bubbles captured in a hybridization region of a microarray, and more particularly, to a method of removing air bubbles captured in an effective region for hybridization using magnetic particles and magnets when a microarray that is covered by a coverslip is hybridized.
2. Description of the Related Art
Microarrays are microchips for biological purposes of analyzing and monitoring gene expressions, gene distributions, mutations by forming an array of hundreds to hundred of thousands of deoxyribonucleic acid (“DNA”), DNA fragments, complementary DNA (“cDNA”), oligonucleotide, ribonucleic acid (“RNA”), RNA fragments, peptide nucleic acid (“PNA”), locked nucleic acid (“LNA”), or the like of which sequences are known on the surface of a small solid substrate made of a material such as surface-modified glass, silicon, nylon or the like.
When biomolecules that can act as a probe are immobilized on the surface of a microarray and a sample for assay is applied to the microarray, the probe can detect specific target biomolecules that are included in a sample. The biomolecules in the sample bind differently with the probe immobilized on the surface of the microarray depending on sequence complementarity or binding affinity, thereby being hybridized with the probe. By detecting and analyzing hybridization, the information on biomolecules such as nucleic acids that are included in the sample can be obtained. In this way, microarrays can be used to obtain extensive information within a short period of time, and thus have been highlighted as an innovative technique that is useful for scientific technique research, new medicine development, clinical diagnosis, agriculture, foods, and environment field, etc.
In an analysis using a microarray, hybridization includes dropping a certain amount of a hybridization solution including a sample on a slide glass with biomolecules such as DNA, etc. immobilized thereon, covering the slide glass by a coverslip to relatively widely spread the hybridization solution and placing and incubating the slide glass-coverslip assembly in a chamber or in an incubator that is maintained at a predetermined temperature.
There exists two major disadvantages in hybridization using a coverslip. One is that an uneven distribution of a hybridization solution on a microarray causing a gradient to form. The other disadvantage is that air bubbles form in the hybridization solution when a hybridization solution is applied to a microarray and then the microarray is covered by a coverslip. In the former case, a sufficiently dimensioned coverslip, such as a Lifterslip™ (Erie Scientific Company, US), may be used such as to distribute the same amount of hybridization solution on each spot of a microarray. For example, edges of both ends of the Lifterslip™ (Erie Scientific Company, US) have a thickness of 0.04-0.06 millimeter (mm), and a hybridization solution is uniformly spread on the surface of the microarray under the coverslip so that the variation in the amount of the hybridization solution per spot can be reduced.
In the case of air bubble formation in the hybridization solution, its severity varies depending upon on the skills and personal states of the practitioner. Absolute solutions to the problem of air bubbles formation have not been found, and therefore caution must be taken not to form air bubbles in the first place. When air bubbles form after a hybridization solution is introduced on a microarray and the microarray is covered by a coverslip, the portion of the microarray on which air bubbles form is not fully reacted with a sample. As a result, some of the sample and a certain part of the microarray are wasted.
In particular, when the microarray is used for clinical assays of patients, air bubbles formed in a hybridization area affect the result, and thus it may cause experimental errors in the clinical examination analysis. According to user manuals of microarray kits that are commercially available from manufacturers such as Agilent, Corning, Telechem, or manuals that are used in national laboratories such as National Institutes of Health/National Human Genome Research Institute (NIH/NHGRI), or universities, it is recommended that caution must be taken not to cause formation of air bubbles in a hybridization solution, and that when air bubbles are trapped, the experiment should be proceeded, while discarding the data from the area where air bubbles formed rather than trying to remove the air bubbles. This procedure is recommended because removing air bubbles included in the hybridization solution beneath the coverslip is difficult, and the difficult-to-obtain sample and expensive microarrays may be wasted while trying to remove the air bubbles.
Therefore, in a process of preparing hybridization, utmost caution is taken by slowly covering the microarray with the coverslip not to form air bubbles, and in the case of air bubbles that cannot be removed, the data from the air bubble formed region is discarded. However, taking into consideration invaluable importance of sample, time and labor consumed for preparing a sample and the expense of a microarray, development of a method of making the most of a microarray by reducing experimental errors is required.